Since a USB transmission interface provides some advantages such as convenience, expandability and high transmission speed in use to users, it is popularly applied to various computer peripherals, information appliances (IAs) or 3C consumer electronics (computer, communications and consumer-electronics). Therefore, the USB transmission interface has become an indispensable transmission interface tool in work and family life to people today. Accordingly, a USB device having the USB transmission interface is popularly applied to storage or memory devices (such as flash devices, MP3 players) and receivers as well.
As described above, the receivers are used for receiving signals sent by a wireless device such as a wireless mouse. In a word, a receiver usually connects with a computer by using a USB transmission interface. In contrary, the wireless mouse is disposed with a transmitter therein. Therefore, commands of the wireless mouse operated by a user are capable of being sent to the receiver of the computer with a form of wireless signal, and then further transmitted to the computer to be read. And thus, the wireless mouse is able to be operated.
The structure of a USB device is exemplarily illustrated hereinafter by a traditional receiver. FIG. 1 illustrates an external structural view of a conventional receiver, FIG. 2 illustrates an internal structural view of a conventional receiver, and FIG. 3 illustrates a structural view of a connecting socket of a conventional receiver. Referring to FIG. 1 and FIG. 2 together first, the conventional receiver 1 comprises a circuit board 10, a body 11 and a metal case 12. The body 11 has a carrying plate 111, the circuit board 10 is disposed within the body 11 and a front end 101 of the circuit board 10 is exposed outside the body 11, and the front end 101 of the circuit board 10 is disposed on the carrying plate 111. The front end 101 of the circuit board 10 is disposed with a plurality of electrical pins 1011, 1012, 1013 and 1014, and the electrical pins 1011, 1012, 1013 and 1014 are respectively a VCC power source circuit, a GND power source circuit, a D+ data transmission circuit and a D− data transmission circuit, wherein the D+ data transmission circuit and the D− data transmission circuit are used for data transmission, while the VCC power source circuit and the GND power source circuit are used for receiving an operating circuit provided by a female connecting socket 2 (as illustrated in FIG. 3) or a power supply.
The metal case 12 encloses the front end 101 of the circuit board 10 in a manner of surrounding, so as to protect the circuit board 10. In addition, an inserting space 112 is formed between the front end 101 of the circuit board 10 and the metal 12, and thus the plurality of electrical pins 1011, 1012, 1013 and 1014 are exposed to the inserting space 112. The inserting space 112 is used for providing a space for fitting the conventional receiver 1 into the female connecting socket 2. In addition, the plurality of electrical pins 1011, 1012, 1013 and 1014 connect with a plurality of connecting pins 21 of the female connecting socket 2 as illustrated in FIG. 3.
As illustrated in FIG. 2, the circuit board 10 disposed within the body 11 further comprises a control circuit 102 and a memory unit 103. The memory unit 103 is used for storing data. Two ends of the control circuit 102 respectively connect with the memory unit 103 and the plurality of electrical pins 1011, 1012, 1013 and 1014 as a control device for transmitting or storing data there-between.
A portion of the body 11 of the conventional receiver 1 except the metal case 12 is defined as a holding portion, and users are capable of holding the conventional receiver 1 via the holding portion. As illustrated in FIG. 1, a length of the holding portion of the conventional receiver 1 is L1, and the length of the holding portion depends on an arrangement of various electrical elements disposed on the circuit board 10 inside the body 11. In general, the conventional receiver 1 is received within the wireless mouse, and the holding portion of the conventional receiver 1 has a certain length, and thus the wireless mouse must have a certain volume for receiving the conventional receiver 1. Therefore, it is unable to meet the requirement of users about the minimization of the wireless mouse in volume. Except for the receiver, it is important to users about the minimization of the USB devices applied to other fields as well. Accordingly, it is desired to provide a USB application device with a smaller volume.